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Re: Why doesn't router remember IP/MAC?

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On 2011-10-27, JimR <NotReallyMyEmail@example.net> wrote:
> One of my main desktops on my home network is Mandriva 2010.2 x86_64.  I 
> have coded it with a static IP address of 192.168.1.107.
>
> This morning, I was running Wireshark, and I noticed this exchange at 
> least twice every minute, ad infinitum.
>
> 23489	4030.195572	Cisco-Li_ea:bf:6a	Micro-St_ab:cd:ef	ARP	Who has 
> 192.168.1.107?  Tell 192.168.1.1	60
>
> 23490	4030.195589	Micro-St_ab:cd:ef	Cisco-Li_ea:bf:6a	ARP	192.168.1.107 
> is at 6c:62:6d:ab:cd:ef	42
>
> Why doesn't the router remember this?

It does -- for a 30 seconds, apparently.

> I would have thought he would have got it once on startup, and then
> retained the information until shutdown.

If that were the case, what would happen if you reconfugured the IP
addresses such that the MAC associated with a 192.168.1.107 changed?

You'd have to restart your router.  People don't like having to do
that, so the router is designed to detect such changes by timing out
stale ARP cache entries after 30 seconds.  The default ARP stale
timeout setting in the Linux stack is 60 seconds.

-- 
Grant Edwards               grant.b.edwards        Yow! I'm pretending that
                                  at               we're all watching PHIL
                              gmail.com            SILVERS instead of RICARDO
                                                   MONTALBAN!

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Why doesn't router remember IP/MAC? JimR <NotReallyMyEmail@example.net> - 2011-10-27 11:32 -0400
  Re: Why doesn't router remember IP/MAC? Grant Edwards <invalid@invalid.invalid> - 2011-10-27 16:58 +0000

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